Does usury apply to private people entering noncommercial loan deals?

If you have two private people, like Joe Six pack, and Polly Purebread who enter a deal. Polly Purebread really wants to go on a cruise with her grand mother. She knows Joe six pack just received a sum of money from his uncle from a trust account. She offers to give him 26% interest on the dollar if he loans her money to make possible for her and her grand mother to go on a cruise. If he accepts, is that an illegal loan deal because of usury constraints, or is that only for entities that loan as a business, like banks, savings and loans, etc? Can private people make whatever interest both parties agree?